The invention relates to a device for continuous drying of material, particularly sewage sludge, which has a belt, particularly a filter belt, on which the material is conveyed. In addition, the invention relates to a process for drying material, particularly sewage sludge, where the material is conveyed on a belt, particularly a filter belt, through a dryer.
Belt dryers have long been used for different purposes. Their disadvantage to date has been uneven distribution of the material on the revolving belt, particularly filter belt, which causes excessive drying of the material in places where the layer was too thin and insufficient drying at other points where the layer was too thick. When paste-like and/or sticky substances, e.g. sewage sludge, are dried, they have to be shaped into particles as close to the same size as possible before being distributed evenly over the belt, particularly a filter belt. This is achieved in plants for sewage sludge according to the state of the art by pressing these substances at high pressure through matrices. Practice has shown that these matrices tend to become clogged due to foreign matter in the product to be dried, which in turn has a very disadvantageous effect on even drying. Furthermore, the dryer has sometimes to be shut down once per shift to clean these matrices. A plant of this type is described in WO 92/00250. This type of plant is also known from EP 0 781 741 B1 or EP 0 889 014 B1. In addition, these systems are highly sensitive to changes in the sludge properties.